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Eighty-one temperature, salinity, dissolved oxygen, turbidity, and fluorescence profiles from Sermilik Fjord and the Southeast Greenland shelf. The temperature, salinity, and dissolved oxygen profiles were collected with a Seabird 25plus conductivity-temperature-depth (CTD) (serial #0251108); the turbidity and fluorescence profiles were collected with a Seabird ECO FLNTU (serial #7748). The profiles were collected during August 2023 from research vessel Tarajoq. The profiles were manually examined and are provided as 1-meter (m) bin averages. The fjord survey was comprised of an along-fjord section and a section spanning the mouth of the fjord. The shelf survey traces the trough that feeds Sermilik. These data were collected as part of a project examining the physical, biogeochemical, and ecological systems of the fjord. The also contributed to a long-term project to monitor Sermilik Fjord to determine what water masses flow into the fjord; in particular, if warm, Atlantic water from the Irminger Sea is able to penetrate into the fjord. Observations have been collected in the fjord since 2008. 

Twelve temperature and salinity profiles from Sermilik Fjord in Southeast Greenland. The profiles were collected using Sippican XCTD-1 eXpendable Conductivity Temperature Depth (XCTD) probes hand deployed from a helicopter. The profiles were collected on July 12, 2023 in the ice mélange of Helheim Glacier and in the northern portion of Sermilik Fjord, including Midgaard Fjord. The profiles were manually examined, quality controlled, and are provided as 2-meter (m) depth bin averaged profiles. These data were collected as part of a long-term project to monitor Sermilik Fjord to determine what water masses flow into and out of the fjord; in particular, if warm, Atlantic water from the Irminger Sea penetrates into the fjord and how freshwater from ice melt is diluted and transported out of the fjord. Observations have been collected in the fjord since 2008. 

This gridded hydrographic data set for Sermilik Fjord was created by objectively mapping (optimally interpolating) discrete hydrographic profile datasets from shipboard Conductivity Temperature Depth (CTD) and helicopter-deployed eXpendable CTDs (XCTDs). These data are all from the summer season (July - September) and cover the years 2009 - 2023 (excluding 2014 and 2020). Grids are standardized to 2 kilometer (km) (horizontal) x 5 meter (m) (depth) resolution grid stretching from 0 km (at Helheim Glacier terminus in 2019) to 106 km away from the terminus following the deepest pathway of bathymetry from the glacier to the shelf (thalweg section). CTD and XCTD profiles were combined to increase along-fjord coverage of the gridded fields. Appropriate gridding parameters and the a priori error were found through a series of manual tests to find a balance between smoothness and hydrographic feature representation (more information in Roth et al. (2025)). The same parameters were used for gridding all variables. Currently the conservative temperature (°C, celsius) and absolute salinity (g kg^-1 (gram per kilogram)) fields, along with their associated mapping relative error, are provided. Other hydrographic variables (eg. dissolved oxygen, nitrate) can be added in the future following the method in Roth et al. (2025) and future surveys of Sermilik Fjord can also be added to increase the time coverage. 

Abstract. As global atmosphere and ocean temperatures rise and the Greenland Ice Sheet loses mass, the glacial fjords of Kalaallit Nunaat/Greenland play an increasingly critical role in our climate system. Fjords are pathways for freshwater from ice melt to reach the ocean and for deep, warm, nutrient-rich ocean waters to reach marine–terminating glaciers, supporting abundant local ecosystems that Greenlanders rely upon. Research in Greenland fjords has become more interdisciplinary and more observations are being collected in fjords than in previous decades. However, there are few long-term (> 10 years) datasets available for single fjords. Additionally, observations in fjords are often spatially and temporally disjointed, utilize multiple observing tools, and datasets are rarely provided in formats that are easily used across disciplines or audiences. We address this issue by providing standardized, gridded summer season hydrographic sections for Sermilik Fjord in Southeast Greenland, from 2009–2023. Gridded data facilitate the analysis of coherent spatial patterns across the fjord domain, and are a more accessible and intuitive data product compared to discrete profiles. We combined ship-based conductivity, temperature, and depth (CTD) profiles with helicopter-deployed eXpendable CTD (XCTD) profiles from the ice mélange region to create objectively mapped (or optimally interpolated) along-fjord sections of conservative temperature and absolute salinity. From the gridded data, we derived a summer season climatological mean and root mean square deviation, summarizing typical fjord conditions and highlighting regions of variability. This information can be used by model and laboratory studies, biological and ecosystem studies in the fjord, and provides context for interpreting previous work. Additionally, this method can be applied to datasets from other fjords helping to facilitate fjord intercomparison studies. The gridded data and climatological products are available in netCDF format at https://doi.org/10.18739/A28G8FK6D (Roth et al., 2025a). All original profile observations, with unique DOIs for each field campaign, are available through the Sermilik Fjord Hydrography Data Portal (https://arcticdata.io/catalog/portals/sermilik, last access: 7 November 2025) hosted by the Arctic Data Center (Straneo et al., 2025). The code used has also been made available to facilitate continued updates to the Sermilik Fjord gridded section dataset and applications to other fjord systems. 

Abstract Cross‐shelf exchange at Greenland's continental margins transports warm waters toward the glacier margins and freshwater offshore into the convective basins of the North Atlantic and Nordic Seas. Several studies have suggested that the exchange is enhanced by the presence of deep, glacial troughs, but observations from Greenland's troughs are scarce. This work presents data from a ship‐based survey at Narsaq Trough, a wide, branched trough in southwest Greenland, during the summer of 2022. We use Conductivity‐Temperature‐Depth‐Oxygen profiles, water samples for nutrient analysis, and underway current profiles to compare the water mass properties and distribution inside and outside the trough, describe the flow‐field in and around the trough, and estimate mixing in the trough. Narsaq Trough is found to provide a pathway for warm, salty Atlantic Water to intrude onto the continental shelf where these waters are mixed with the overlying cold, fresh Polar Water. As a result, waters in the trough are fresher, oxygen‐enriched, macronutrient‐depleted, and at times colder, relative to the unmodified Atlantic Water offshore. This trough‐modified water has the potential to freshen and oxygenate the flow on the shelf‐break and/or reduce the thermal forcing of waters in the adjacent fjord, limiting ice melt. 

Abstract Watermass transformation in the Irminger Sea, a key region for the Atlantic Meridional Overturning Circulation, is influenced by atmospheric and oceanic variability. Strong wintertime atmospheric forcing in 2015 resulted in enhanced convection and the densification of the Irminger Sea. Deep convection persisted until 2018, even though winters following 2015 were mild. We show that this behavior can be attributed to an initially slow convergence of buoyancy, followed by more rapid convergence of buoyancy. This two‐stage recovery, in turn, is consistent with restratification driven by baroclinic instability of the Irminger Current (IC), that flows around the basin. The initial, slow restratification resulted from the weak horizontal density gradients created by the widespread 2015 atmospheric heat loss. Faster restratification occurred once the IC recovered. This mechanism explains the delayed recovery of the Irminger Sea following a single extreme winter and has implications for the ventilation and overturning that occurs in the basin. 

Abstract The Greenland Ice Sheet is losing mass at an accelerating pace, increasing its contribution to the freshwater input into the Nordic Seas and the subpolar North Atlantic. It has been proposed that this increased freshwater may impact the Atlantic Meridional Overturning Circulation by affecting the stratification of the convective regions of the North Atlantic and Nordic Seas. Observations of the transformation and pathways of meltwater from the Greenland Ice Sheet on the continental shelf and in the gyre interior, however, are lacking. Here, we report on noble gas derived observations of submarine meltwater distribution and transports in the East and West Greenland Current Systems of southern Greenland and around Cape Farewell. In southeast Greenland, submarine meltwater is concentrated in the East Greenland Coastal Current core with maximum concentrations of 0.8%, thus significantly diluted relative to fjord observations. It is found in water with density ranges from 1,024 to 1027.2 kg m⁻³and salinity from 30.6 to 34, which extends as deep as 250 m and as far offshore as 60 km on the Greenland shelf. Submarine meltwater transport on the shelf averages 5.0 ± 1.6 mSv which, if representative of the mean annual transport, represents 60%–80% of the total solid ice discharge from East Greenland and suggests relatively little offshore export of meltwater east and upstream of Cape Farewell. The location of the meltwater transport maximum shifts toward the shelfbreak around Cape Farewell, positioning the meltwater for offshore flux in regions of known cross‐shelf exchange along the West Greenland coast. 

Abstract Fresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of freshwater enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much freshwater is mixed into the overturning circulation’s deep limb in the present day. To constrain these freshwater pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Freshwater sources are split into oceanic Polar Waters from the Arctic and surface freshwater fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv (1 Sv ≡ 10 6 m 3 s −1 ) of the total 110 mSv of surface freshwater fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic freshwater outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.